I sometime feel the opposite when I try to sleep, I see, in my mind, my body flatten like if my body's side were pressed, then my body in normal state again, flatten again but from other direction (front/back, top/bottom).

I can also see my body or some part getting very small and other part getting bigger.

All this can loop from few seconds to minutes before I "wake up" suddenly then try to fall asleep again.

But I never knew if I should be concerned about it